logsync

// first some boilerplate setup
ctx, done := context.WithCancel(context.Background())
defer done()

// our example has two authors. Johnathon and Basit are going to sync logbooks
// let's start with two empty logbooks
johnathonsLogbook := makeJohnathonLogbook()
basitsLogbook := makeBasitLogbook()

wait := make(chan struct{}, 1)

// create a logsync from basit's logbook:
basitLogsync := New(basitsLogbook, func(o *Options) {
	// we MUST override the PreCheck function. In this example we're only going
	// to allow pushes from johnathon
	o.PushPreCheck = func(ctx context.Context, author identity.Author, ref dsref.Ref, l *oplog.Log) error {
		if author.AuthorID() != johnathonsLogbook.Author().AuthorID() {
			return fmt.Errorf("rejected for secret reasons")
		}
		return nil
	}

	o.Pushed = func(ctx context.Context, author identity.Author, ref dsref.Ref, l *oplog.Log) error {
		wait <- struct{}{}
		return nil
	}
})

// for this example we're going to do sync over HTTP.
// create an HTTP handler for the remote & wire it up to an example server
handleFunc := HTTPHandler(basitLogsync)
server := httptest.NewServer(handleFunc)
defer server.Close()

// johnathon creates a dataset with a bunch of history:
worldBankDatasetRef := makeWorldBankLogs(ctx, johnathonsLogbook)

items, err := johnathonsLogbook.Items(ctx, worldBankDatasetRef, 0, 100)
if err != nil {
	panic(err)
}
fmt.Printf("johnathon has %d references for %s\n", len(items), worldBankDatasetRef)

// johnathon creates a new push
johnathonLogsync := New(johnathonsLogbook)
push, err := johnathonLogsync.NewPush(worldBankDatasetRef, server.URL)
if err != nil {
	panic(err)
}

// execute the push, sending jonathon's world bank reference to basit
if err = push.Do(ctx); err != nil {
	panic(err)
}

// wait for sync to complete
<-wait
if items, err = basitsLogbook.Items(ctx, worldBankDatasetRef, 0, 100); err != nil {
	panic(err)
}
fmt.Printf("basit has %d references for %s\n", len(items), worldBankDatasetRef)

// this time basit creates a history
nasdaqDatasetRef := makeNasdaqLogs(ctx, basitsLogbook)

if items, err = basitsLogbook.Items(ctx, nasdaqDatasetRef, 0, 100); err != nil {
	panic(err)
}
fmt.Printf("basit has %d references for %s\n", len(items), nasdaqDatasetRef)

// prepare to pull nasdaq refs from basit
pull, err := johnathonLogsync.NewPull(nasdaqDatasetRef, server.URL)
if err != nil {
	panic(err)
}
// setting merge=true will persist logs to the logbook if the pull succeeds
pull.Merge = true

if _, err = pull.Do(ctx); err != nil {
	panic(err)
}

if items, err = johnathonsLogbook.Items(ctx, nasdaqDatasetRef, 0, 100); err != nil {
	panic(err)
}
fmt.Printf("johnathon has %d references for %s\n", len(items), nasdaqDatasetRef)

Output:
johnathon has 3 references for johnathon/world_bank_population
basit has 3 references for johnathon/world_bank_population
basit has 2 references for basit/nasdaq
johnathon has 2 references for basit/nasdaq